An inkjet printing apparatus is used for printing an image on a printing medium by ejecting ink from a printing unit (a printing head), and has the advantage that downsizing of the printing unit is easy and an extremely fine image can be printed at a high speed. Furthermore, because printing can be performed even on plain paper without needing any specific processing, the inkjet printing apparatus also has the advantage that the running cost is low. In addition, there are the advantages that the inkjet printing system is a non-impact printing system and therefore noises are small, and that the printing system can easily be applied to applications for printing color images using multiple color inks.
In the inkjet printing apparatus, often a pressure is utilized for carrying out processing within the apparatus. (Refer to, for instance, Patent Documents 1 to 3).
For instance, in printing apparatuses in which an ink is successively supplied from an ink storage section (an ink tank section) in response to a printing operation (ejection of ink), there are some apparatuses in which, when no ink remains in an ink tank by printing, and the ink tank is exchanged with a new one. In this case, to again fill an ink supply path up to the printing head with an ink, a process for sucking the ink is performed by applying a pressure (a negative pressure) lower than the atmospheric pressure to a face of the printing head (referred to as “ejection face” hereinafter) on which ink ejection openings are provided.
Furthermore, there are inkjet printing apparatuses in which a cleaning unit (also referred to as “restoring unit”) for cleaning a printing head is provided for obtaining excellent image quality by maintaining or restoring the ink ejecting operation in or to the stable state. This cleaning unit has mainly two mechanisms. One of the mechanisms is a wiping mechanism for wiping off dust, or droplets of water or ink deposited on the ejection face, and this mechanism relatively moves a wiping member (also referred to as “blade” or “wiper”) made of an elastic material such as urethane rubber and having a plate-like form while the wiping member is contacted to the ejection face. Another one is a mechanism for resolving clogging caused by fixation of ink inside an ejection opening or for any other reason, and a pressure is used for this mechanism. For instance, clogging is resolved by applying a negative pressure to the ejection face to forcibly discharge the ink from the ejection opening.
[Patent Document 1] Japanese Patent Laid-Open No. 2000-118000
[Patent Document 2] Japanese Patent Laid-Open No. 2001-138545
[Patent Document 3] Japanese Patent Laid-Open No. 2004-284189